courtyard/asphalt driveway

[machmeter62]

Gentlemen:
We have a concrete courtyard that rises 6" above the long asphalt driveway that is connected to the slab The courtyard is now gated with two 6' x 8' hinged gates that swing outward 180 degrees. I want to merge that 6" rise down to the existing asphalt driveway with concrete, with maybe some kind of decorative imprint to enhance the looks? I have seen this merged else where, but don't know the technique?

My concern is how "thin/thick" should I, or can I pour any concrete on top of the existing asphalt,(or must it be removed first?) from the gated area as it approaches the long driveway four feet away. There is already 3/8" rebar 12" oc length/width for the entire 16' of the gated area...perpendicular to the concrete slab without it cracking out. The existing "adjacent asphalt" area has been there 20+ yrs. without cracks or settlement.

This home is in a rural area that requires propane trucks, and maybe septic ones on occasions also, to transverse that 6" slab. Thanx in advance for your help and other ideas?

 

[beenthere]

I think cutting out the asphalt and removing any that will be under the concrete for the best job.

 

[Gary Fowler]

It shouldnt be a problem pouring concrete over asphalt if it is not heaving or cracking. You wont get a better base than asphalt to pour your concrete on. You just need to be able to put at least 3" of concrete down. I would use the nylon fiber reinforced type and avoid any rebar placement if you just need a thin slab. If you pour 4" so you can have 2" on each side of any rebar or wire reinforcement, then you could use wire or bar but you need at least 2 " of concrete cover over any bar or wire. The fiber reinforced concrete, you can place without internal wire or bar over your asphalt base. The fiber helps avoid shrinkage cracking and can replace the rebar in your situation.
I wouldnt remove the good asphalt base unless you have some height limitation that keep you from putting in a minimum of 3" thick slab.

 

[Western]

I've seen allot of parking lots drilled a ton of holes in them, I have seen asphalt on concrete, but never seen concrete on asphalt so can't honestly answer that one. I don't know if I would want any moisture trapped between the 2 substrates.

What I would do. I would remove the asphalt, build up the base near the existing slab and pour a 4" slab with re-bar. I would also either get a joint material or joint adhesive, (both available at the box stores) for a space between the existing slab and the new pour.

I have used fiber reinforced and I know, at least here where I am, they still recommend the use of steel with fiber if there will be weighted traffic. Here also they have steel fiber reinforced concrete that supposedly does not require re-bar, in fact, the owner of the major concrete company here supposedly poured his new 5000' house using the steel fiber without re-bar.

Personally I'd rather spend $200 or so bucks on steel now than deal with it later.

Just my 2 cents.

 

[Egon]

If you want a nice smooth gradual merged joint some asphalt will have to go so you can get a proper thickness of concrete at the joint.:thumbsup:

 

[gwjd]

aparently its called white toping

Ultra-thin Whitetopping (UTW) - Pavement repair with Concrete Overlays Over Asphalt

also the MO DOT has been milling off the old layers of asphalt on the interstates to a smooth level surface then placing a layer of geo textile then pouring 6-8 inches of concrete on top of that works out great but they are milling down to old concreat with a little asphalt left on ruts and such

it appears that the asphalt needs to be on a sound base and the concrete 4 inch thick for best results

my worry is you will have to cut a trench to allow a smooth transition and i see the joints cranking

also how many asphalt drives are on a sound base if it were me is would rip it out put in a few inches of compacted base and pour a slab as thick as the other concrete you can use the ruble for rip rap on the property